Variable condenser



R. CROCKER VARIABLE connmisrm Jul as, 41925. 1,541,412

Filed Kay 8. 1922 Mm; o O I fl]? H Patented July 28, 1925.

UNITED STATES PATENT OFFICE.

ROY GROGKER, OF VVINLOCK, WASHINGTON.

VARIABLE Application filed May 8,

To all whom it may concern:

Be it known that I, ROY CRooKER, a citizen of the United States, and aresident of lVinlock, county of Lewis, and State of Washington, haveinvented a new and useful Variable Condenser, of which the fol lowing isa specification.

The present invention relates to improvements in variable condensers andwhile adapted to be used for general purposes is designed particularlyfor use in connection with radio receiving sets. The principal object ofthe present invention is to provide a variable condenser of simpledesign, practically indestructible, with a fixed dielectric and withmeans associated therewith which hold a sheet of conductive materialforming one of the plates of the condenser under continuous tension.

)Vith these objects in View I have illustrated the preferred form of myinvention in the accompanying drawing, in which Figure 1 shows a sideelevation of my condenser; Figure 2 a top plan view of the same; Figure3 a vertical cross section through the principal working part of thesame, and Figure 4 a side elevation of a modified form. While I haveshown only the preferred form of the invention, it should be understoodthat various changes or modifications may be made within the scope ofthe claim hereto attached without departing from the spirit of theinvention.

The base (1), which may be made of wood or any other suitable material,is provided with two standards (2) of insulating material disposed inspaced relation to each other and furnishing bearings for the shafts (3)and (4) of two rolls (5) and (6) disposed in parallel relation to eachother. Both rolls and their shafts are made of conducting material andthe roll (5) is covered peripherally with a sheet (7) of mica or anyother suitable dielectric material.

A wide flexible sheet (8) of conducting material is secured to bothrolls so that it may be wound from one roll on the other or vice versaby turning one of the rolls by means of the knob (10). The latter sheetis preferably soldered to the metallic roll (6), as shown at (9) so asto make a good metallic connection with the same and is secured to theroll (5) by means of a plate (11) placed on the sheet, and screws (12)penetrating the CONDENSER.

1922. Serial No. 559,278.

plate and the sheet and extending into a strip (1a of insulatingmaterial embedded in the roll so that the sheet is insulatec from thelatter roll.

To prevent buckling of the sheet (8) and to maintain the same undertension, I provide a second elastic band (16) between the two rolls, thetension of the elastic sheet opposing any tendency of the metallic sheetto buckle.

The condenser is connected into a circuit by means of the two bindingposts (17) and (18) to which the lead wires (19) and (21) may be securedand from which the wires (22) and (23) lead to the plates (24) and (26)making metallic connection with the two shafts (3) and (4) respectively,as shown at (27) and (28).

Since only one fixed sheet of dielectric is provided around the roll (5)it is not desired that the latter roll be free to make more than onerevolution, and means for limiting the rotary motion of this roll aretherefore provided in the stop (31) secured to one of the standards (2)and a radial projection (32) extending from the shaft (3) and strikingthe stop on a left hand as well as on a right hand turn.

The operation of the device thus far described will be readilyunderstood. The conducting roll (5) furnishes one plate of the condenserand the flexible sheet (8) furnishes the other plate, with the micaacting as a dielectric. Since the capacity of a condenser isproportional to the area of the dielectric interposed between twoplates, the capacity of this condenser will vary according to the lengthof the flexible sheet (8) wound on the dielectric or on the roll (5).The elastic band (16) serves to maintain the flexible sheet (8) underconstant tension and the stop (31) prevents the roll (5) from beingturned too far which might cause the over-stretching of the same.

Any suitable material such as glass, sulphur, or enamel, may be used fora dielectric and the fact that the'dielectric is permanently and fixedlysecured to the roll (5) will prevent oreepage or slipping between thesame and the plates. The device may be adapted to be used with high orlow voltage by changing the thickness of the dielectric.

In Figure 1 is shown a slightly modified form in which the roll ismounted in stationary bearings while the roll (6) is journaled inupright members (34:) pivota-lly secured to the base (36), as shown atThe shaft (38) of the latter roll is engaged by it forked member (39),the free end of which is connected to a stationary standard (41) bymeans ofaspring 42), which latter tends to pull the shaft (38) away fromthe roll andto thus co-operate with the band (16), which in this caseneed not be made of elastic mate rial in securing proper tension for theconducting sheet (8).

I claim: 7

A Variable condenser comprising two conducting rolls of substantiallyequal diame ter mounted in spaced and parallel relation, a dielectricperipheral cover for one of the rolls, a flexible conducting sheetsecured to both rolls to bridge corresponding points thereof and adaptedto be wound and unwound from the roll covered by the dielectric and anelastic band bridging the rolls in opposing relation to the sheet formaintaining the latter under tension.

ROY OROCKER.

